9
Top-Down Controls
Bottom-Up Controls
SALMON
BIOLOGICAL
INTERACTIONS
PATHOGENS/
DISEASE
MARINE
MAMMALS
SALMON
AQUACULTURE
SALMON
HATCHERIES
SALMON HABITATS
& CONTAMINANTS
WILD
SALMON
GROWTH &
SURVIVAL
Forage Fish Base
Ichthyoplankton
Zooplankton
Phytoplankton
Physical & Chemical
Oceanography
ANNUAL WEATHER VARIATION
Figure 2. A schematic of the factors addressed annually within the Salish Sea Marine Survival Project. In aggregate, studies within each
of these components made up the SSMSP.
HYPOTHESES (CAUSE AND EFFECT)
Science advisors to the SSMSP agreed that the primary ecological processes to investigate included:
A. Bottom-up processes — annual environmental conditions that determine the food for salmon and therefore
result in the variation in size and growth rate of juvenile salmonids.
B. Top-down processes — biological processes that directly determine the survival of salmonids. Predation is likely
the direct cause of mortality, but fish condition may be compromised by other biological factors, increasing their
susceptibility to predation (e.g., disease, hatchery versus wild competition).
C. Additionally, indirect factors exacerbating these ecological processes, including habitat loss and contaminants.
What distinguish the SSMSP from previous efforts are the scope of topics considered simultaneously and the breadth
of collaboration involved. Put simply, the SSMSP endeavored to study everything at once that could be hypothesized
to impact the annual production of Pacific Salmon within the Salish Sea (Figure 2); as opposed to individual interests
in separate species, years and locations.
Our intention is to determine whether the causes of weak Chinook, Coho and steelhead survival are locally
(e.g., runoff, wastewater, marine mammal management, habitat availability, hatchery production) or globally-driven
(climate change, ocean acidification, ocean cycles). Better understanding of local impacts has the potential to inform
action-oriented management decisions to improve salmon production in the Salish Sea; whereas better understanding
of globally-driven impacts will further our knowledge about how best to adapt to the changing environment.
1. The original focus in Canada was on the loss of Chinook and Coho catches, but in Puget Sound, Steelhead trout are also a significant concern.
Production of steelhead trout in southern BC has also declined in recent decades but has not received the same attention as declines of Chinook
and Coho Salmon.
2. The Southern Resident Killer Whale population is listed as 'endangered' under Canada's Species at Risk Act (http://www.registrelep-sararegistry.gc.ca/
default.asp?lang=En&n=A9748209-1). See map: http://staff.wwu.edu/stefan/SalishSea.htm
3. A "smolt" is the stage of a juvenile salmon's life when it is physiologically capable of adapting to saltwater. In this stage, the juvenile becomes silvery
(losing it dark bars) and begins migration out of freshwater habitats.
